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994                             Appendix V.

boiler, the dimensions of the boiler and the main results of the
tests being as follows :—

Dimensions.

One central cylinder, 42" diameter.
375 small tubes, 3" diameter.
Outside diameter of casing, n' 2".
Height of central cylinder, 22' 2".
Total heating surface, 3129 square feet.
Feed heater consists of 180 ft. of 2%' pipe, area being 141 sq.
feet, heating the water from 451° to 80° F.

The Test..

Duration     ...        ...        ...        ...        ...    8 hours.

Dry coal per hour, best Welsh     ...        ...    1057 Ibs.

Calorific value        ............    14,886 B.T.U.

Temperature of chimney gases     ...        ...    593° F.

Feed per hour        ...        ...     * ...        ...    10,234 Ibs.

Steam pressure       ...        ...        ...        ...    192 Ibs.

Steam superheated from    .........    384° to 455°.

Horse power (at 34J Ibs. evaporation)     ...    297.

Thermal efficiency...        ...        ...        ...    79*31%.

Water evaporated per Ib. of dry coal from

and at 212°   ...        ...        ...        ...j

12*22 Ibs.

From these figures it will be seen that the boiler stands high
for efficiency. At the same time steam can be raised very
rapidly, a gauge pressure of 125 Ibs. having been obtained in ten
minutes, while in other cases sudden changes from 10 to 500
H.P. have been met without as much as a pound variation by
gauge. Repairs are said to be slight, tubes being kept automatic-
ally free of deposit by reason of the rapid circulation, and all
mud is easily removable from bottom of central cylinder, where it
falls. Economy of floor space is, of course, self-evident